Geoscience Reference
In-Depth Information
break the degeneracy between size and distance under certain conditions
when a cylindrical symmetric solution and a center-crossing event were
assumed. It is not clear whether this will still be the case with a more
complete parameter space when certain photometric error or noise is con-
sidered. Starting from the theory of diffraction, an ensemble of light curves
can be derived with a specific astronomical distribution and/or astrophys-
ical model assumed. These light curves will be fed into a data pipeline for
photometric analysis and e
ciency test. The output of this simulator can
be compared with an observational result, which will be a test against the
astronomical/astrophysical model assumed earlier. Details and progress of
our simulator and some additional comments on a simple geometric model
are presented in Sec. 3.
2. Taiwan
America Occultation Survey Status
and Zipper Mode Test
The objective of TAOS is to simultaneously monitor thousands of stars in a
field with three or four robotic telescopes running in synchronous mode at
a rate of 5 Hz (the rate can be varied). This rate corresponds to a shadow
of a few kilometers in size passing through a specific site at a relative speed
around 25 km/s, which is dominated by the orbital velocity of the earth
itself. These four dedicated small (50 cm) telescopes have a wide field of view
(1
.
7
◦
×
−
1
.
7
◦
). The use of at least three telescopes is to reduce false positives
below a statistically significant threshold.
17
,
18
While having the telescopes
separated by several kilometers would have provided better resolution and
the possibility to determine size and shape directly, practical considerations
have lead to have all the telescopes operating at one site within a hundred-
meter range. Follow-up observation with a larger telescope could be helpful
in telling a foreground asteroid event apart.
Instead of using a multi-object photometer
15
or fiber optics, a high-
quantum eciency, back-illuminated CCD camera (SI-800) with 2048
×
2048 pixels
b
was installed on each telescope. Following the experience from
the ROTSE project,
19
control software has been developed which can per-
form a sky patrol automatically. A special function which can respond to
a gamma-ray-burst coordinates network (GCN) alert was also integrated
with the software. Given the high data rate of TAOS, each telescope might
b
There are actually four more rows unmasked. Some of them have different sensitivities.
